Finally got the new 451 running in the '68 Satellite. Just took an easy slow drive around the back lot to get a feel for the brakes. Only problem is, now the stopping power is not as good as it was when the car was running with the small block. Before the brakes felt great and the car stopped well. This is at 15-20 mph doing a panic stop just to check things out.
BEFORE:
360 ci motor (no vacuum measurement taken)
904 auto
Aftermarket brake pedal linkage with aftermarket 8" dual diaphragm booster and adjustable push booster push rod fully retracted for minimal MC engagement
Adjustable proportioning valve present, incorrectly installed between MC and brass distribution valve, but adj prop valve dialed all the way back to zero (effectively providing approximately 57% reduction in a specified pressure range, i.e. for panic stops)
Stock firewall reinforcement backing plate missing
Brake booster vacuum hose running to back of Edelbrock carb
AFTER:
451 ci motor with mild cam, measured 14 inches vacuum
727 big block auto
Stock brake pedal linkage (pedal now sits lower to floor) with aftermarket 8" dual diaphragm booster and adjustable push booster push rod adjusted to protrude approximately 1" adjusted for correct MC engagement
Adjustable proportioning valve no longer present, only brass distribution block for disc/drum
Stock firewall reinforcement backing plate
Brake booster vacuum hose running to intake manifold fitting behind carb
SAME FOR BOTH:
Same Raybestos 15/16" bore disc/drum Master Cylinder
Same wilwood forged dynalite front disc calipers
same stock rear drums
same vacuum brake booster
RESULT:
Brake pedal now sits lower, half as high as before
Brake pedal feels slightly softer
Braking power seems reduced. On a panic stop at 15-20mph, brakes were not grabbing hard and car seemed to take too long to come to a complete stop. If I didn't know any better, I might even think only the rears are doing all the work...
Any ideas as to what may be going on? Does my new motor's increased displacement have anything to do with it? How about the booster hose connection location change from carb to intake??
BEFORE:
360 ci motor (no vacuum measurement taken)
904 auto
Aftermarket brake pedal linkage with aftermarket 8" dual diaphragm booster and adjustable push booster push rod fully retracted for minimal MC engagement
Adjustable proportioning valve present, incorrectly installed between MC and brass distribution valve, but adj prop valve dialed all the way back to zero (effectively providing approximately 57% reduction in a specified pressure range, i.e. for panic stops)
Stock firewall reinforcement backing plate missing
Brake booster vacuum hose running to back of Edelbrock carb
AFTER:
451 ci motor with mild cam, measured 14 inches vacuum
727 big block auto
Stock brake pedal linkage (pedal now sits lower to floor) with aftermarket 8" dual diaphragm booster and adjustable push booster push rod adjusted to protrude approximately 1" adjusted for correct MC engagement
Adjustable proportioning valve no longer present, only brass distribution block for disc/drum
Stock firewall reinforcement backing plate
Brake booster vacuum hose running to intake manifold fitting behind carb
SAME FOR BOTH:
Same Raybestos 15/16" bore disc/drum Master Cylinder
Same wilwood forged dynalite front disc calipers
same stock rear drums
same vacuum brake booster
RESULT:
Brake pedal now sits lower, half as high as before
Brake pedal feels slightly softer
Braking power seems reduced. On a panic stop at 15-20mph, brakes were not grabbing hard and car seemed to take too long to come to a complete stop. If I didn't know any better, I might even think only the rears are doing all the work...
Any ideas as to what may be going on? Does my new motor's increased displacement have anything to do with it? How about the booster hose connection location change from carb to intake??